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President Barack Obama spoke to family members during a ceremony at the Pentagon on the anniversary of the Sept. 11 attacks. "Today we remember a day that began like so many others," he said. (Published Tuesday, Sept. 11, 2012)

Updated at 12:50 PM EDT on Thursday, Nov 15, 2012

The nation paused Tuesday for the 11th anniversary of the 9/11 attacks, marking the occasion with services that were more modest than years past, a reflection of time's passing and the continued need to reflect and heal.

New York's ceremony was held at the National September 11 Memorial, in the shadow of One World Trade Center, which will open in 2014 at 104 stories tall. The somber ritual remained largely the same, with victims' families reading the names of the nearly 3,000 victims. They stopped for moments of silence at the times when airliners struck the World Trade Center and the Pentagon and crashed into a field in western Pennsylvania, and when the towers collapsed.

Looking Back: The Nation Reacts to the 9/11 Attacks

The one big change was the exclusion of speeches from elected officials in a politically charged year.

In Washington, President Barack Obama and First Lady Michelle Obama gathered on the White House lawn for a moment of silence. Later, at the Pentagon Memorial, the president said America remains stronger because of the attacks.

9/11 Anniversary Remembered

"As painful as this day is and always will be, it leaves us with a lesson, that no single event can ever destroy who we are, no act of terrorism can change what we stand for," Obama said.

He added, "that's the commitment that we reaffirm today. That's why, when the history books are rewritten, the legacy of 9/11 will be not hate or division but a safe world, and people united more than ever before."

He mentioned the killing of Osama bin Laden and other al Qaida leaders, as well as the end of the war in Iraq and the ongoing withdrawal of troops from Afghanistan.

He also acknowledged the abiding grief of victims' families.

"No matter how many years pass, no matter how many times we come together on this hallowed ground, know this: that you will never be alone, that your loved ones will never be forgotten."

Scaled-down services at the Washington National Memorial replaced the larger commemorations of prior anniversaries. Around downtown Washington, meanwhile, hundreds of volunteers took part in a "day of service and remembrance."

Following his remarks at the Pentagon, President Obama headed to Arlington National Cemetery, where he and the First Lady walked among graves marking recent war dead, the Associated Press reported. They stopped at a headstone that honors 10 members of the military and Drug Enforcement Administration who were killed in a helicopter crash in Afghanistan in 2009, according to NBC News.

The president planned to visit Walter Reed National Military Medical Center to visit wounded service members.

Both Obama and his Republican opponent, Mitt Romney, lifted their negative advertising on Tuesday and refrained from any overt political statements.

Romney marked the anniversary with a speech to the National Guard Association Conference in Nevada, in which he praised service members who have fought in the two wars sparked by 9/11, and those who killed Osama bin Laden.

He called for renewed investment in the military, and better care and support for returning veterans.

"We will not forget why they are fighting or who they are fighting for," Romney said.

In Shanksville, Pa., Vice President Joe Biden and Interior Secretary Ken Salazar visited the Flight 93 National Memorial, where the last hijacked plan crashed after the terrorists were overrun by passengers. The service included a moment of silence and the reading of the victims' names.

Biden described the passengers' actions as the embodiment of heroism: "individual acts of heroism by ordinary people in moments that could have been contemplated."

He went on: "Like all the families, we wish we weren't here. We wish we didn't have to be here. It's a bittersweet moment for the entire nation, particularly for those family members gathered here today."

The 11th anniversary brought renewed focus on the delayed development of memorials in New York and Shanksville.

Construction of a $1 billion museum at the World Trade Center site stalled for months as public officials fought over how to finance it. Late on Monday, New York Gov. Andrew Cuomo announced that he, New York City Mayor Michael Bloomberg, New Jersey Gov. Chris Christie and the Port Authority of New York and New Jersey had reached an agreement to restart work.

In Shanksville, officials said they needed another $5 million to complete a learning center, visitors center and a Tower of Voices to honor the 40 victims who died there.

Salazar vowed that the project would be completed.

"We are getting close, we will get it done," he said.

The 11th anniversary arrived amid lingering concerns about the health of emergency workers who breathed toxic fumes and dust at the attack sites.

Some estimates put the number of illness-related deaths at over 1,000. Tens of thousands more are being treated for various ailments. New York City firefighters are among those suffering the worst; the Fire Department continues to add names to its roster of 9/11 dead. Police officers and other workers have died of cancer in recent weeks.

The debate over how to distribute $2.7 billion in federal victim compensation funds continues as well. The list of cancers covered in the funding law keeps gets longer; 14 new types were added on Monday.